The invention is concerned with a marine structure. In particular it is concerned with installing, particularly with suction force e.g. generated by a so called suction pile, and the design of an anchoring body in the subsea bottom. The invention is both relative to the anchoring body and the installing device and the combination of both and is also relative to the method of installing.
With this anchoring body horizontal and/or vertical loads can be taken up from an object to be anchored in or above the subsea bottom, such as an oil production platform floating in or on the water or a vessel or a mooring buoy for a vessel or a subsea pipe line. The anchoring body can be part of a plurality of horizontal spaced anchoring bodies provided within the soil and from each of which an anchoring line extends upward to a floating object, such as an oil production platform (a so called tension-leg platform; viz. e.g. WO96/40548, incorporated here by reference). The anchoring body can be integrated with the installing device, or be coupled therewith in a easily disengageable manner.
The design and installation of an anchoring body with the aid of a suction pile is e.g. described in WO98/52819 and in GB-A-2317153 (corresponding to the British patent application, filing number 19960001894, titled xe2x80x9cA Subsea Mooringxe2x80x9d, in the name of Karel Karal), both incorporated here by reference. Both describe coupling of the anchor and the suction pile on a ship deck above seal level, lowering the combination onto the subsea bottom, sucking in of the upright suction pile into the subsea bottom such that the upright anchor completely disappears into the subsea bottom and therewith is completely embedded by the subsea bottom, disengaging the anchor from the suction pile and pressing the suction pile upward from the subsea bottom by internal over pressure to relocate it onto the ship deck. The anchor is coupled to a flexible anchor line extending therefrom until above the subsea bottom. This anchor line follows such a path through the subsea bottom and the water there above, that this is exclusively adapted to transmit a horizontal load onto the anchor. Since the anchor is separate from the suction pile it is possible to install the suction pile completely below the subsea bottom.
Suction piles and their way of installing are o.a. known from GB-B2300661 and EP-B-0011894, which disclosures are incorporated here by reference. Briefly, a suction pile is a thin walled steel cylinder, closed at at least one longitudinal end, that is located on the subsea bottom with the opposite end and penetrates the subsea bottom with the aid of a suction created within the cylinder. The creation of the suction can be with the aid of a suction source, such as a pump, being on, or close to or at a distance (e.g. above the water surface, e.g. at a vessel) from the suction pile. The applied level of the suction can be e.g. at least substantially constant, smoothly increase or decrease or else pulsate; for which there are convenient means; for an e.g. pulsating level a possibly in the suction pile integrated pressure accumulator that is After use, the suction pile can easily be removed by creating an overpressure within the cylinder, e.g. by pumping in (sea) water.
According to one aspect installing is concerned of an in embedding-direction profiled anchoring body, i.e. a body that is preferably not flat sheet like as viewed in embedding direction, but shows more of e.g. a wave or bulge, or is preferably assembled from mutually angularly connected parts, or has an in itself closed shape, such as a ring shape, wherein said shape is preferably adapted such that said body gets support from the inner wall of the suction pile and/or the lower side of the suction pile or the suction pile requires no additional implements to at least tilting free holding said anchoring body. In this manner it is e.g. not necessary that the anchoring body penetrates the sideway boundaries of the suction space substantially, which e.g. results in an at its lower side diametrically oppositely over about half the height of the anchor notched suction pile with a notch width about equal to the anchor plate thickness. It is also e.g. not necessary in that sense that the suction pile penetrates the anchoring body with e.g. a boundary from above.
In one aspect the concern is the installing of the anchoring body in the subsea bottom wherein the body remains at least substantially fixed in position, this contrary to the known installing wherein after bringing to a convenient depth into the subsea bottom, the body experiences tilting, e.g. by pulling thereon via a so called bridle, to become active.
In one aspect the concern is to give the anchoring body the desired configuration within the subsea bottom by means of a tension or compression force provided by e.g. the suction pile during its pressing out the subsea bottom. E.g. a wedge is activated or an extendable part is extended by it, from which the anchoring body gets its anchoring power at least partly, preferably at least substantially.